Based on the selective colocalization of the A2AR and D2 dopamine receptor in the striatopallidal neurons and their antagonistic functional interaction in the striatum, the adenosine A2AR antagonist has been pursued for improving the motor symptoms of PD in recent decades; it has finally received approval in the US and Japan for the treatment of adult PD patients experiencing OFF time who are currently taking levodopa (plus a decarboxylase inhibitor) [51,52]. The gene discussed is DRD2; the disease is Parkinson disease.